A lithium phosphate-based compound has significantly excellent stability due to a structural feature even in a case in which short-circuit or over-heating of a battery occurs. A lithium phosphate iron-based compound having an olivine structure may be prepared using a cheap raw material and have high bulk density and excellent thermal stability and life characteristics, such that the lithium phosphate iron-based compound has been commercialized as a cathode active material.
However, in a lithium composite phosphate salt having an olivine structure, lithium ions may be diffused only in one direction, such that research for improving a diffusion rate of lithium has been conducted as in International Patent NO. WO11/132930.